Flotation apparatus



Oct. 25, 1938.

M; KRAUT 2,134,410

FLOTATION APPARATUS A TTORNEY Patented Oct. 25, 1938 FLOTATION APPARATUS Max Kraut, San Francisco, Calif. Application September 28, 1936, Serial No. 102,948

21 Claims.

This invention relates to flotation apparatus for the recovery of mineral values from ore pulp, and more particularly relates to such an apparatus in which a rising column of pulp in transit 5 through the apparatus is subjected to aeration above the general level of the pulp body in the apparatus.

In order to clearly understand the objectives.

of the present apparatus it is necessary to consider present day flotation machines, particularly machines of the mechanical type. Among the essential functions which must be satisfactorily performed by pulp flotation apparatus may be mentioned the need for a thorough agitation of the pulp; that is, thorough mixing of the pulp with reagents; also circulation of the pulp for maintaining in suspension the solid particles in the pulp, and the transfer of the pulp along from one flotation unit to the next one in order, in situations where a plurality of units are employed; another desired function is the dissemination of an abundant supply of air throughout the mass of the pulp to provide a necessary condition for successful flotation of the mineral particles and to form a flotation froth. In the known mechanically operated machines it has.

been the endeavor to accomplish these functions by the single device of an agitator, rotor or impeller, generally submergedin the pulp at the bottom end of a rotating shaft. It is here ob.

served that itis new and novel in this art to I provide a single device that will carry out all of the foergoing functions efliciently since, in the known art, they interfere with each other in varying .degrees. The amount of air which can be disseminated into the mass of pulp is largely a function of the peripheral speed attained by the agitator, rotor, or impeller; that is, the greater the speed, the more air will be forced into the pulp. However, admission of air too freely into the impeller or rotor interferes very seriously with the agitation and circulating capacity of the device and may reach the point when agitation and circulation are actually reduced to such an extent as to cause sanding-up of the flotation receptacle and interfere with the proper operation of the apparatus. As a consequence, it is necessary to limit the admission of air so as not to interfere with the circulation of the pulp to an extent which will reduce efliciency. Therefore, the known'devices have heretofore been a compromise between aerators and agitators which do not serve with greatest efllciency as either one or the other. It must be further ob served that the aeration of the pulp at the bottom of a pulp column againstthe resistance of the body of the pulp column is necessarily inefficient and consumes an excessive amount of power. It follows that the aeration of thepulp is accomplished with a'much greater degree of efliciency if they discharge of the pulp from the rotor device is free and without resistance.

In the present invention various mechanisms for accomplishing the several functions have been separated in-sucha manner that'each function will be accomplished in a different part of the apparatus without interference with the functional efllciency of the respective mechanisms.

r With the foregoing explanation of the problems which are overcome by this invention, one of the objects of the invention is to provide a flotation apparatus of greater mechanical and metallurgical emciency, with relatively low power consumption which will effect the highest obtainable metallurgical recovery of the the economic mineral values in. a pulp body. Another object is to provide a flotation apparatus in which a pulp mass is aerated in proximity to, and preferably above, the upper level of the pulp body in the apparatus. Stillanother object is toprovide in a flotation apparatus a mechanism which will deposit aerated pulp in close proximity to the upper level of the pulp mass'in the apparatus.

With the foregoing and other objects in view, all of which will be more apparent as this .description proceeds, the invention is exemplified 'in one form in the novel construction and combination of parts hereinafter described, illustrated in the accompanying drawing, and-pointed out in the claims hereto appended, it being understood that various changes in the form, proportion, size and details-of construction of the apparatus may be resorted to within the scope of the appended claims.without departing from the spirit or sacrificing any of the advantages of the invention.

To more clearly comprehend the invention, reference is directedto the accompanying drawing wherein:

Fig. 1 is a plan view of a pair of cells or flotation units employing this invention.

Fig. 2 is a combined front elevational view of one, of the units of Fig. 1 and a vertical transverse sectional view of the other flotation unit of Fig. 1, as indicated by line II-H in Fig. 1.

Fig. 3 is a lateral transverse vertlcal'section Ion lineIII- -III of Fig. 1.

Fig. 4 is an enlarged side view of'aeration apparatus shown in the other views, and. being partly broken away and partly in section to show detail of structure, as viewed at line IV--IV of Fig. 5.

.Fig. 5 is a plan view of the apparatus of Fig.

4, partly broken away and in section to illustrate detail of structure.

In more fullydescribing the invention, reference is made to the accompanying drawing illustrating a preferred form which the invention may take and in which like characters of reference indicate corresponding parts in the several views. There is provided a tank or container, generally indicated In of any suitable size and shape, which is'illustrated herein as generally cylindrical. A suitable supporting frame ll extends upwardly from the cylindrical'portion of the tank and, as herein illustrated, comprises an upward extension of a portion of the tank wall for about one-half the circumference of the tank, the opposite vertical edge portions l2 being connected by cross bars I3 which mounting other mechanism.=

The tank ID has an inwardly and downwardly inclined conical bottom l4 provided with a central drain plug I 5. Within the tank and mounted on the conical bottom I4 is a conical hollow feed chamber it which has aplurality of perforations or apertures l1 adjacent its base in close proximity to the bottom l4 and providing communication between the interior of the tank l and the interior of the conical member. Hi. The

wall of the conical feed chamber I5 supports, as at l8, a cylindrical vertical pipe l9 whichis open at both ends and has its lower end in spaced relation to the inclined bottom l4. Within the pipe I9 is rotatably mounted a vertical shaft having at its lower end a pump impeller 2| of suitable standard design, for vertically impelling pulp from the feed chamber Ii through pipe I9. Shaft 20 is suspended from a bearing housing generally indicated 22 which has therein an upper antifriction shaft-bearing 23 and a "similar lower shaft-bearing 24, said bearing housingebeing supported on the brackets l3 as by the plates 25. The shaft 29 is rotated by means of a headpulley 25 which is belt-driven from any suitable power source, such as motor 21, and its,attendant drive-pulley28.

Mounted on the vertical shaft 20 below the lower bearing 24, but well above the pulp level in the apparatus, is an aerating device 29 which overlies the outlet end opening of the vertical pipe I 9 and which rotates with shaft 20 to which it is secured by suitable means, such as pins 39. This aerating device 29, which is preferably formed of slightly resilient, tough rubber to facilitate molding and resist abrasion, comprises a horizontal circular top disc 3|v having a downturned annular flange or side wall 32 and is open at its bottom due to its being of greater internal diameter than the outer diameter of pipe l9. On the inner circumference wall of this annular flange 32 there are circumferentially arranged a plurality of relatively spaced blades 33 which are inclined from the vertical at an angle, preferably about 45, from the upper to the lower part of the flange in' a direction of inclination opposite to the direction of the rotation of the aerating device 29, so that the upper portion of the blade is forward and the bottom portion rearward.

The radially inward edge of these blades is incllned radially outwardly from top to bottom so that the blades are wider at their upper portion than at their lower portion as best indicated at 33 and 33 of Fig. 4. These blades 33 may, if

preferred, be slightly arcuate as shown in the serve as brackets for cross-section of Fig. 4. Through the top disc 3| of the aerating device 29 there is provided a series of holes or apertures 34, preferably cylindrical and extending completely through the disc plate 3| and opening into the interior of the aerating device slightly forward of the upper portion or lead edge of each blade 33. These holes 34 are inclined radially outwardly and downwardly from near the center of the top face of the disc 3| to the bottom face of the disc, in a direction opposite to the direction of rotation of the aerating device 29. and is concentric with the upper open end of pipe l9. At the bottom of blades 33 is a collar l9 which may serve as a wearing strip around thetop of pipe l9 and being spaced from flange 32 providing the openings 29 at the lower ends of blades 33 so that the aerated pulp is thrown downwardly through the openings 29 and radially outwardly from pipe 19.

A cylindrical hood 35is supported on the hearing housing 22 and is vertically adjustable relative thereto by means of collar and set screw 35. The hood 35 is open at the bottom and is of greater length than the aerating device 29 to which it is in close proximity relative to the outer flange wall, but with suflicient space between to provide'an operating clearance. The cylindrical The flange or side wall 32 overhangs hood 35 is provided on its inner side adjacent 'a portion of which underlies the respective circumferences of the aerating device and the skirt of the hood. The pan 39 has vertically adjustable mounting on the pipe l9 by any suitable means of adjustment, such as set screws 49. At the bottom of the groove of the pan 39 there is provided a series of small apertures 4|.

A suitable standard air inlet valve 42is mounted in the upper conical portion 35 of hood 35, by which regulated entry of air within the hood is provided, since the air force at the opposite open end of the hood is downward due to the action of the aerator 29.

The top. edge of the tank I0 is formed on a downward incline from back to front as best shown in Fig. 3, and the upper opening of the tank is partially closed by a plate 44 which has an upstanding collar 45 providing a central upper opening 46 of the tank of lesser diameter than the lower portion of the tank. The plate 44 and collar 45 cooperate with the upwardly extended portion I 2 of the tank to form a launder 41 as best shown in Fig. 2. The plate 44 preferably extends forwardly beyond the circumference limit of the tank as at 49, and the launder may be completed at the side edges of the plate 44 by supplemental walls 49.

A feed chute 50 of any suitable type-may be employed for feeding pulp to the tank under the feed chamber l5 through the feed pipe 5|.

It is to be understood that these flotation units are preferably installed in a bank consisting of a plurality of individual units, it being provided that the pulp which is returned from the aerating device intbthe body of the tank l0 may flow through the perforations of the apertures I! rew sponsive to the action of the impeller 2| and be again treated in the same tank, or, may flow out of the tank through the opening 52 through. a

weir 53 in the direction shown by the arrows in Fig. 2 and into the feed pipe 5| of the next following flotation unit. A weir-gate 54 is provided in the weir to, regulate the height of the pulp level in the tank, and at which height the pulp will flow through the weir from one unit to the next succeeding unit. The weir 53 may'also be provided adjacent its base with an auxiliary opening 55 which may be suitably controlled by. any type of valve apparatus or shut-off'56 for the purpose of preventing sanding-up at the bot tom of the weir.

In operation .the properly ground and diluted pulp, to which the requisite amount of collecting,

preferred that the total area of all of the amt tures in chamber l6 shall be relatively less than the capacity of the impeller so that a degree of forced suction flow will be established through the apertures l1, since this will provide sufficient velocity to the flow of pulp through chamber Hi to prevent sanding-up in that chamher. The discharge of the pulp from the pipe i9 due to the resistance of a pulp column, a very large amount of-air is induced intothe pulp ly overflows the outer lip is under and within the rotating aeration device 29. The rotating inclined blades 33 in the aeration device rend the discharged pulp column erful vertical downward motion .through the openings 29 by gravity. Because-of the free discharge of the pulp from the aerating device at high velocity, there being no retarded motion through the holes 34 in the disc 3|. The effect of the outward and downward inclination of the openings 'or holes 34 is that they not only have a tendency to scoop in air at the upper face of the disc 3|, but by reason of the relatively greater circumferential path of travel of the lower ends of the holes 34 at the inner orbottom face oi! .the disc 3| as compared with opposite ends of the holes at the top of disc 3|, there is a suctioncreated which greatly facilitates and increases the air that is taken in under the aerating device. The amount of air admitted may be regulated by means of the air inlet valve 43 located on top of the hood-35. An undesirable rotative movement of the pulp, as it is thrown downwardly from the aerating device through openings 29, is prevented by means of the baflies 31 on the inside of the skirt of hood 35. The downward dis-- charging aerated pulp strikes the U-shaped pan 33 with considerable force which breaks the velocity of the pulp and at the same time causes a thorough dissemination of the entrained air throughout the mass of the pulp. The larger bulk of the aerated pulp having been brought to a relatively quiescent state in the pan 39 gent- ;Iacent and-slightly above the pulp level in the apparatus, and spreading over the surface of the pulp permits the air bubbles laden with mineral particles to collect and form a mineral froth concentrateabove thepulp level which, when accumulated in suflicient volume overflows the edge of the tank into the concentrate launder of the pan closely ad- 41. A small part of the pulp passes through the opening 4| in the bottom of the pan 39 and carries with it any detritus which may accumulate in the pan, and thereby prevents the pan from sanding-up. I

It must be observed that in this apparatus the air bubbles carrying the mineral load do not have to rise through and overcome the resistance of a high pulp column with a chance of dropping the mineral load 'inthe procedure; but due to the fact that the bubbles-collect on or near the surface, the chance of losing the mineral load is reduced to a minimum and the metallurgical and mechanical efliciency of the apparatus is to be enhanced. It will be further observed that those air bubbles which do partially sink into the mass of pulp in the tank are disposed in the upper layer of the pulp body in the tank so that they have a tendency to rise to the surface much more rapidly than if the aerated pulp were dispersed throughout the pulp body in the tank.

The demineralized pulp, after it has passed through the aeration device, slowly sinks to the bottom of the tank and either flows through the openings I! under the support member Hi, from where the cycle of retreatment is repeated, or

else flows through the opening 52 at the discharge side of the tank from where it may rise to the controlled pulp level and overflow weirgate 54 andmay enter the next cell or unit for retreatment. The demineralized pulp, after having passed through a sufficient number of cells is finally discharged as a tailing product from the last in a series of such units and may be suitably disposed of as waste. into minute particles and impart thereto a powtainer for a pulp mass; means for elevating pulp ,i'r'om said container to above the upper level of the pulp mass in. the montainer, means for aerating the elevated pulp solely above the upper level of the pulp mass, a separate skirt extending downwardly from the aerating means toward the pulp level and adapted for directing the aerated pulp from the aerating means to the pulp mass in the container, and an annular grooved pan underlying the discharge portion of the aeration means, said pan having a discharge edge above the pulp level in the tank container for discharging the aerated pulp above the upper level'of the pulp mass in the container.

. 2. A flotation apparatus including a tank container for a pulp mass, means for elevating pulp from saidcontainer to above the upper level of the "pulp mass in the containenmeans separate from the elevating means for aerating the elevated pulp above the upper level of theqpulp mass, and a separate skirt extending downwardly irom the aerating means toward the pulp level and adapted for directing the aerated pulp from the aerating meansto the pulpmass in the container, and an annular grooved pan underlying the discharge portion of the aeration means, said. pan having a discharge edgeabove the pulp level in the tank container for discharging thev aerated pulp mass in the container, and an annular grooved pan underlying the discharge portion of the aeration means, said pan having a discharge edge above the pulp level in the tank container for discharging the aerated pulp above the upper.

' level of the pulp mass in the container.

4. A flotation apparatus including a tank container for a pulp mass, means for elevating pulp from said container to above the upper level of the pulp mass in the container, means for aerating the elevated pulp above the upper level of the pulp mass, said aerating means comprising a disc top and a depending flange having blades extending radially inwardly therefrom and inclined from bottom to top in the direction of rotation of the disc, a separate skirt extending downwardly from the aerating means toward the pulp level and adapted for directing the aerated pulp from the aerating means to the pulp mass in the container, and an annular grooved pan underlying the discharge portion of the aeration means, said pan having a discharge edge above the pulp level in the tank container for discharging the aerated pulp above the upper level of the pulp mass in the container.

, 5. A flotation apparatus including a tank container for a pulp mass, means for elevating pulp from said container to above the upper level' pulp mass in the container, and an annular grooved pan underlying the discharge portion of the aeration means, said pan having a discharge edge above the pulp level in the tank container for discharging the aerated pulp above the upper level of the pulp mass in the container.

6. A flotation apparatus including a tank container for a pulp mass, means for elevating pulp from said container to above the upper level of the pulp mass in the container, and rotatable means separate from the elevating means for aerating the elevated pulp above the upper level of the pulp mass, said aerating means comprising a disc top and a depending flange having blades extending radially-inwardly therefrom and inclined from bottom to top in the direction of rotation of the disc, a separateskirt extending downwardly from the aerating means toward the pulp level and adapted for directing, the aerated pulp from the aerating means to the pulp mass in the container, and an annular grooved pan underlying the discharge portion of the aeration -means, said pan having a discharge edge above "7. flotation apparatus including a tank container for a pulp mass, means for elevating pulp from said container to above the upper level of the pulp mass in the container, and rotatable means separate from the elevating means for aerating the elevated pulp above the upper level of the pulp mass, said aerating means compristhe aeration means, said pan having a discharge edge above the pulp level in the tank container for discharging the aerated pulp above the upper level of the pulp mass in the container.

8. A flotation apparatus including a tank container for a pulp mass, means for elevating pulp from saidcontainer to above the upper level of the pulp mass in the container, means for aerating the elevated pulp above the upper level of the pulp mass and a panv underlying the aeration means and adapted to receive aerated pulp therefrom, said pan having a discharge edge above the pulp level of the tank container.

9. A flotation apparatus including a tank container for a pulp mass, means for elevating'pulp from said container to above the upper level of the pulp mass in the container and rotatable means separate from the elevating means for aerating the elevated pulp above the upper level of the pulp mass and a pan underlying the aeration means and adapted to receive aerated pulp therefrom, said pan having a discharge edge above the pulp level of the tank container.

10..A flotation apparatus including a tank container for a pulp mass, means for elevating pulp from said container to above the upper level of the pulp mass in the container including a verticallydisposed conduit having an inlet end and an outlet end and means for impelling a body of pulp therethrough, rotatable means overlying the outlet end of said elevating means and adapted for aerating the elevated pulp above the upper level of the pulp mass, and a pan underlying the aeration means and adapted to receive aerated pulptherefrom, said pan having a discharge edge above the pulp level of the tank container, and said aerating means including means for deflecting aerated pulp from the aerating means back into the said underlying pan.

11. In a flotation apparatus which includes a tank for containing a pulp mass, a vertically disposed pipe conduit in said tank having an inlet end opening and an outlet end opening and means for elevatinga body of pulp through the pipe conduit, an aerating means overlying the outlet end opening of said pipe conduit and adapted for aerating the elevated pulp-above the upper level of the pulp mass, said aerating .means having a radially outer portion of greater diameter than the vertical pipe conduit, said radially outer portion including a plurality of blades rotatably mounted about a common axis of rotation and being inclined downwardly and rearwardly from their upper to their lower portion in relation to the direction of rotation of said blades, said blades being adapted for deflecting and impelling pulp vertically downwardly toward the pulp mass in cailydilposed pipe conduit.

- the tank outside the circumference of the verti- 12. In a flotation apparatus which includes a tank for-containing a pulp mass, a vertically disposed conduit in said tank having an inlet end opening and an outlet end opening and means for elevating a duit, an aerating means-overlying the outlet end opening of said pipe conduit and adapted for aerating the elevated pulp above the upper level of the pulp mass, said aerating means having a radially outer portion of greater diameter than the vertical pipe conduit, said radially outer portion including a plurality of blades rotatably mounted about a common axis of rotation and bea ing inclined downwardly and rearwardly from 'for elevating a conduit, an aerating means overlying the outlet upper portion to lower portion in relation to the direction of rotation of the blades, and being adapted for deflecting and impelling aerated pulp vertically downward toward the pulp mass in the tank outside the circumferences of thevertically disposed conduit, the said aerating means including a top plate overlying said blades, said top plate having apertures therein for admitting the entry of air adjacent to said blades.

13. In a flotation apparatus which includes a tank for containing a pulp mass, a vertically disposed pipe conduit in said tank having an inlet end opening and an outlet end opening and means body of pulp through the pipe end opening of said pipe conduit and adapted for aerating the elevated pulp above the upper level of the pulp mass, said aerating. means including a top and a down-turned side wall having its radially outer portion of greater diameter than the vertically disposed pipe conduit and a plurality of blades in said radially outer portion and between said top and the outlet end opening of the pipe conduit, said plurality of blades being rotatable about a common axis of rotation and said respective blades being inclined downwardly and rearwardly from their upper to their lower portion, with relation to the direction'of rotation of the blades, and adapted for deflecting aerated pulp vertically downwardly toward the pulp mass in the tank outside the circumference of the vertically disposed pipe conduit.

14. In a flotation apparatus which includes a tank for containing a pulp mass, a vertically disposed pipe conduit in said tank having an inlet end opening and an outlet end opening and means for elevating a body. of pulp through the pipe conduit an aerating means overlying the outlet end opening of saidpipe conduit and adapted for aerating the elevated pulp, said aeratin means comprising a top and down-turned side wall having its radially outer portion of greater diameter than the vertically disposed pipe conduit and a plurality of blades in said radially outer portion and between said top and the outlet end opening of the pipe conduit, said aerating means having apertures therethrough for admitting entry of air thereunder, and said blades being rotatable about a common axis of rotation and said respective blades being inclined downwardly and rearwardly from their upper to their lower portion, with relation to the direction of rotation of the blades.

15. In a flotation apparatus which includes a tank for containing a pulp mass and means for elevating pulp from the tankincluding a vertically disposed pipe conduit in said tank having an inlet end opening and'an outlet end opening,

a rotatable aerating means overlying the outlet end opening of said pipe conduit-and adapted for aerating the elevated pulp above the upper level pending side wall body of pulp through the pipe con-' an inlet end opening and aerating means pipe'conduit in said tank ing a body of p p overlying the outlet opening of said of the pulp mass, said aerating means comprising an apertured body having a top and a deenclosure of .said side wall and rotatable therewith, the apertures of said body being adapted for admitting air under the top of the aerating means.

16. In a flotation apparatus which includes a and having blades within the tank for containing a pulp mass and means for elevating pulp from the tank including a vertically disposed pipe conduit in said tank having an outlet end opening, a rotatable aerating means in overlying relation to the outlet end opening of said pipe conduit and adapted for aerating the elevated pulp above the upper level of the pulp mass, said comprising a disc top and a depending flange side wall havingits radially outer portion of gre vertically disposed pipe conduit and having blades under said top and withi'rrthe said radially outer portion of the confines of theside wall, said blades being inclined downwardly and rearwardly from top to bottom relative to the direction of rotation of the aerating means.

1'7. In a flotation apparatus which includes a tank for containing a pulp mass and means for elevating pulp from the tank including a vertically disposed pipe conduit in said tank having an inlet end opening and an outlet end opening, a rotatable aerating means in overlying relation to theoutlet duit and adapted above the'upper aerating means for aerating the elevated pulp level of the pulp mass, said comprising an, apertured body having a top and a depending flange side wall and having blades under said top and within the confines of said side wall, said blades extending radially inwardly from the side wall-and being infrom top to bottom relative to the direction of rotation of the aerating means.

18. A flotation apparatus includinga tank for containing a pulp mass, a vertically disposed pipe conduit in said tank having an inlet opening and an outlet opening, rotatable aerating means in overlying relation to the outlet opening of said pipe conduit and adapted for aerating the elevated pulp solely above the upper level of the pulp mass, said aerating means comprising an apertured body having a top and depending flange side wall and having blades under said top and within theconflnes of the side wall, and aseparate skirt extending downwardly from the aerating means ed for directing the aerated pulp from the aerating means to the pulp mass in the container, the said blades of the aerating means being inclined downwardly andrearwardly from top to bottom relative to the direction of rotation of the aerating means.

19. A flotation apparatus including a tank for containing a pulp mass, a vertically dipsosed having an inlet opening and an outlet opening and means for impelltherethrough, rotatable aerating means separate from-the elevating means toward the pulp level and adaptpipe conend opening of said pipe conduit and adapted for aerating the elevated pulp above the upper level oi the pulp mass, and a separate skirt extending downwardly from the aerating means ed for directing ing means to the pulp mass in the container, said aerating means including a plurality of blades on toward the pulp level and adaptthe aerated pulp from the aeratits under side adjacent the said pipe outlet opening and inclined downwardly and rearwardly from upper to lower portion relative to direction of rotation of the aerating means.

20. A flotation apparatus including a tank container for a pulp mass. a vertically disposed pipe conduit in said tank having an inlet opening andan outlet opening, and means for impelling a body of pulp therethrough, rotatable aerating means overlying the outlet opening of said pipe conduit and adapted for aerating the elevated pulp above the upper level of the pulp mass, said aerating means comprising an apertured body having a top and depending flange side wall and having blades under said top and within the confines of the side wall, and a separate skirt extending downwardly from the aerating means toward the pulp level and adapted for directing the aerated pulp from the aerating means to the pulp mass in the container, the apertures in the body of the aerating means and the blades of said aerating means being inclined relative to the axis of rotation of said aerating means.

21. A flotation apparatus including a tank container for a pulp mass, means for elevating pulp from said container to above the upper level of'the pulp mass in the container, including a vertically disposed pipe conduit having an inlet opening and an outlet opening and means for impelling a body of pulp therethrough, rotatable aerating means overlying the outlet opening of the elevated pulp above the upper level of the pulp mass, said aerating means comprising a body having a disc top and a depending flange side wall, and having blades extending radially 5 MAX KRAUT.

said elevating means and adapted for aerating inwardly from the side wall and inclined downthe aerating means toward the 

